To simplify a process and reduce costs at the time of an aluminum (Al) metal process ranging from 0.18 μm technology to 0.13 μm technology, a photo process may be performed without using a BARC layer used in some related art photo processes.
Instead of using an ARC layer, a method of processing Hexamethyldisilazane (HMDS), coating a photoresist on metal, such as TiN, and then forming patterns of the photoresist may be used.
HMDS may have a chemical structure of (CH3)3Si—NH—Si(CH3)3. The method may improve adhesive force between the substrate and the photoresist through a chemical reaction of oxygen (O) coupled on a Si substrate and HMDS.
HMDS may serve to change hydrophilicity to the lipophilic property, and may be limited to prevent a sliding phenomenon of the photoresist due to notching.
FIG. 1 is a view illustrating a related art reaction mechanism between HMDS and a silicon wafer.
Referring to FIG. 1, HMDS may be one of silane coupling agents and may have a lipophilic organic functional group at one side and a methoxy group or an amine group, that is, a functional group. HMDS may be used to change the surface properties of a wafer.
A surface of the wafer may be processed by using HMDS. The surface of the wafer may then be changed to an organic property by (CH3)3Si, as illustrated in FIG. 1.
FIG. 2 illustrates a related art photo process and FIG. 3 is a SEM photograph illustrating a photoresist in a related art photo process.
Referring to FIGS. 2 and 3, when only HMDS is processed on TiN and an exposure process is performed, sidewalls of photoresist 10 may not have a uniform profile when photoresist 10 is patterned. This may be because TiN may have an amine group in structure.
In the related art, if an ARC layer is not used, light may be reflected from the substrate surface and the reflected light may reach both sidewalls of photoresist 10. Thus, a standing wave phenomenon in which the sidewalls of photoresist 10 may not be uniform may be generated.
If erroneous alignment of the photoresist is generated or if an error occurs in a CD target at the time of the photo process, a rework of the photo process may be carried out. In this case, ashing employing O2 plasma may be generally performed.
FIGS. 4 to 6 illustrate a process of performing a rework at the time of a photo process and FIGS. 7 and 8 are SEM photographs illustrating a photoresist collision phenomenon.
A photoresist with an alignment error or a photoresist in which errors occur in a CD target may be removed. An O2 plasma ashing process may then be performed.
Referring to FIG. 5, the surface of the wafer may be oxidized by the O2 plasma ashing process, and specific oxide 20 may be formed on TiN.
Referring to FIG. 6, since photoresist 10 for forming via holes or contact hole may not be adhered to the surface of the wafer at the time of a metal process, a problem may occur in that photoresist 10 may be inclined.
In other words, as shown in FIGS. 7 and 8, at the time of the rework of the photo process, the wafer surface may be oxidized and the photoresist having an oxidization property may not adhere to the wafer surface. Consequently, the photoresist may be inclined.
This may degrade the characteristics of the semiconductor device, and may also increase the manufacturing cost of the semiconductor device.